During well testing procedures after a well has been drilled and completed. The well is typically flowed under a wide range of flow conditions, including the condition of maximum flow. Wells that have been completed may not flow to the surface due to insufficient formation pressure or formation pressure may be considerable to thus induce flow of petroleum products at an extremely high rate. For example, it is not unusual for wells to flow at a maximum rate of 4,000 barrels of oil per day during flow testing. It is necessary, therefore, to provide a testing valve mechanism that is capable of functioning properly at a wide range of well flow conditions, including conditions of extremely high flow rate. In every case, it is necessary that the valve mechanism be capable of absolutely shutting in the well when valve closure is accomplished.
In the past, various types of downhole valve mechanisms have been employed during well testing activities. The typical valve employed for this service is a conventional annulus pressure operated drill string testing tool. Such tools typically have the disadvantage that tubing conveyed perforation activities can not be carried out with initial reservoir pressure measurements taken before opening the downhole valve. It is desirable to provide a shuttle valve mechanism that enables tubing conveyed operations to be carried out either by a drop bar mechanism or by means of an electrical wet connector. Annulus pressure operated DST valves typically function as normally open valves which are operated by application of annulus pressure. For greater efficiency and better safety it is desirable to provide a DST valve that is designed to act as a normal enclosed valve such as it closes automatically upon dissipation of formation pressure utilized to maintain it in an open condition.
Conventional drill string testing tools are normally open valves that are placed in the well or are then actuated by application of annulus pressure. The condition of such valves during installation provides significant insecurity that could be overcome by providing a normally closed drill string testing valve.
It is therefore a principal feature of the present invention to provide a normal drill string testing valve that is in the form of a shuttle valve that is capable of efficient movement between open and closed positions to provide for efficient well control under all flow conditions including conditions of well flow at extremely high rates.
It is another feature of this invention to provide a novel drill stem testing valve that is installed in the well in a hydraulically locked closed condition for purposes of safety and, after being installed, it easily hydraulically unlocked to provide the valve with the capability of being opened for flow test procedures by application of annulus pressure.
It is a further feature of this invention to provide a novel drill stem testing valve that is capable of efficient and safe closure at extremely high rates of well flow.